Cationically polymerizable resin compositions containing an epoxy resin, etc., have excellent adhesion strength, sealing properties, high strength, heat resistance, electrical characteristics, and chemical resistance, and thus have been conventionally used for various applications, including adhesives, sealants, potting agents, coating agents, electrically conductive pastes, and the like. In addition, the applications have a wide variety of targets. Particularly in electronics, they have been used for semiconductors, flat panel displays such as liquid crystal displays, organic electroluminescence, and touch panels, hard disk devices, mobile terminal devices, camera modules, and the like.
Patent Literature 1 (JP 59-204676 A) discloses a photo-cationically polymerizable resin composition containing an epoxy resin and a photo-cationic initiator that generates a Lewis acid upon active energy ray irradiation, such as UV irradiation. In addition, Patent Literature 2 (WO 2005/059002 A) discloses a cationically curable epoxy resin composition containing an epoxy resin composition, a photo-cationic initiator, a thermal cationic initiator, and a filler.